Prior to this invention, various smoke detectors have been proposed such as the ones described in U.S. Pat. No. 4,004,288 which issued to William Webb Jr. on Jan. 18, 1977, U.S. Pat. No. 3,950,739 which issued to James P. Campman on Apr. 13, 1976, U.S. Pat. No. 3,313,946 which issued to B. G. Goodwin et al on Apr. 11, 1967, U.S. Pat. No. 3,255,441 which issued to B. G. Goodwin et al on June 7, 1966, U.S. Pat. No. 4,119,419 which issued to Anthony Passaro on Oct. 10, 1978, U.S. Pat. No. 3,469,250 which issued to R. H. Voigt on Sept. 23, 1969 and U.S. Pat. No. Des. 238,484 which issued to Roy R. Ludt on Jan. 20, 1976.
Many of the previously proposed smoke detectors are designed for permanent installation on walls or ceilings. These detectors are usually bulky and cannot conveniently be carried by a person from one location to another for temporary use in such places as motel and hotel rooms. A portable type of cordless, battery-powered detector has also been proposed as shown in the above Campman patent. The Campman detector is provided with a flashlight type casing so that it can be carried more easily in a person's pocket. This gas detector, however, is specifically constructed for use while being carried in a person's hand and is not designed in such a manner that it can conveniently be placed for use in rooms on flat furniture surfaces or the like.